Our region leads the way for innovative stormwater runoff solutions in the arid Southwest. Low impact development (LID) is an approach that uses soils and vegetation to manage stormwater by mimicking natural water flow to retain and use stormwater for multiple environmental and community benefits. Green infrastructure (GI) is an urban planning practice that includes engineering techniques, structures and components that puts LID principals into action, such as mitigating stormwater flooding and pollutants to create safer and more comfortable streets.

Looking at LID and GI in semi-arid climates is necessary because the main body of literature and policy has originated in wetter climates in the eastern United States. In the U.S. Environmental Protection Agency document entitled, “Green Infrastructure (GI) in Arid and Semi-Arid Climates,” the Tucson region was used as an example as a growing LID community.

PAG created a resolution highlighting the economic, health and transportation safety benefits of Green Infrastructure (GI) and re-affirming the importance of using stormwater as a water resource for our region. A task force suggested the creation of the resolution comprised of support from jurisdictions across the region, Working Group members, and representatives from various fields of expertise representing each issue.

The Green Infrastructure Prioritization Tool can help decision-makers allocate limited financial resources and support GI efforts. The interactive map, accessible below, contains multiple layers for you to explore the relationships between environmental conditions and social demographics. Available data layers include regional tree canopy, surface temperature, extreme heat vulnerable populations, USDA food deserts, the Tucson Bikeways map and water flow lines. This exercise can help you determine the heat reduction benefits when higher levels of shade trees are present as a result of enhanced stormwater management for improved regional mobility and livability.

Green infrastructure provides habitat, reduces the urban heat island effect, adds cooling and shading to urban neighborhoods and improves air quality. Stormwater harvesting keeps yard chemicals on site, treating pollutants biologically in runoff through soil processes and slows flood water which otherwise would be conveyed through the streets and into desert washes. GI also prevents water from running into the streets, where it can pick up pollutants that are then transported into washes.

Broad-based implementation of rainwater harvesting could reduce municipal water demand by reducing the need for potable water for irrigation, which accounts for over a third of household water use in Tucson. Local PCRFCD modeling has shown that broad-scale green infrastructure implementation could result in decreased floodwaters and reduced erosion near culverts and other flood control devices in drainage areas.

Each of these benefits has been studied to measure the monetized metrics of their impacts. The U.S. Environmental Protection Agency has found that, in most cases, implementing well-chosen LID practices saves money for developers, property owners and communities while protecting and restoring water quality and helps property owners to meet LEED green building requirements.

A multi-partner, collaborative study conducted in 2013 and 2014 found that investing in green infrastructure (GI) or low impact development (LID) approaches for infrastructure projects will lead to cost-savings that benefit the community, municipalities and the private sector. As part of best tests for this study, two local projects were tested to evaluate the impact of a “green streets” policy and local commercial stormwater harvesting ordinance. The analysis of the return on investment covered the full life cycle of the projects. The study also evaluated specific local design standards. Results of the study were used to enhance the recommended design strategies in the Pima County LID Guidance Manual.

PAG provided metrics specific for desert regions that showed the cost benefits associated with water conservation and transportation projects that incorporate GI/LID practices.

Study partners included PAG, the Pima County Regional Flood Control District and City of Tucson, Impact Infrastructure LLC and Stantec.

AutoCASETM Beta Testing Project: Evaluation of GI/LID Benefits in the Pima County Environment*

An analysis of green infrastructure policies and programs in the region was conducted in the summer of 2012. Over 70 policies, programs and other efforts were documented and showed that municipal support of GI/LID has increased steadily since 1985.

Water resources in the PAG region include groundwater, Central Arizona Project water, surface water, reclaimed water (effluent reuse) and stormwater. The region depends on water to sustain urban, agricultural and mining interests as well as natural habitat.

PAG’s Watershed Program coordinates with local governments to discuss concerns and works to effect change at the state level as needed.

The Tucson region places a priority on preserving important habitat, wildlife corridors and critical linkages while continuing to grow and meet development demands. Pima County recently developed a long-term vision for protecting the region's heritage and natural resources through its Sonoran Desert Conservation Plan. Critical Habitat, biological corridors and riparian protection were some of the main features evaluated as part of this study.

Both the Town of Marana and the City of Tucson are working on their respective Habitat Conservation Plans, which propose conservation measures to aid the preservation needs of specific species. This work has been conducted in response to listings or potential listings of species under the Endangered Species Act.